JPH0256375A - Device for detecting medium - Google Patents

Abstract

PURPOSE:To detect the existence of a medium while simultaneously distinguish the type thereof in a thermal transferring recording device by making media reflect the radiating light from a light emitting element and receiving the reflected lights each having different reflecting angle by a plurality of light receiving elements. CONSTITUTION:A medium detecting device 2 has a light emitting element 3 for radiating a radiating light L1 with an incident angle theta1 to a medium 1, a light receiving element 4 for receiving a reflected light L2 with a reflecting angle theta2 (theta2=theta1), and a light receiving element 5 for receiving a reflected light L3 with a reflecting angle theta3 (theta3>theta1). When a medium of high irregular reflection, e.g., an ordinary sheet of paper 1a comes in, since the spreading angle phi1 of irregular reflection is approx. 80 deg., the intensities of irregular reflections L2, L3 which both light receiving elements 4, 3 receive are higher than a defined level causing each detected signal to be H. On the other hand, when an OHP sheet 1b of low irregular reflection comes in, the spreading angle phi2 of irregular reflection is approx. 20 deg., causing only the light receiving element 4 to output H while leaving the output of the light receiving element 5 at L. Thereby, the type of a medium can be also detected enabling the quality of printing to be kept constant.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to printers that use different types of media such as plain paper and OHP sheets (sheets for overhead projectors), thermal transfer recording devices, electrophotographic printers, and photocopiers. The present invention relates to a medium detection device installed in a machine, etc.

<Prior art> In printers, etc., a medium detection device (hereinafter simply referred to as a detection device) detects the presence or absence of a medium being fed to a printing unit, and also detects the leading edge of the medium in progress and starts printing. controlling the position. One of these medium detection devices is a light reflection type detection device using a light emitting element and a light receiving element.

FIG. 6 is a schematic diagram showing a conventional example of this type of detection device.
5 is a diagram seen from the front in the running direction of the medium 51. FIG. As shown in the figure, the detection device 52 includes a light emitting element 53 such as an LED and a light receiving element 54 such as a phototransistor, and has pixel elements 53 and 54 arranged in a plane perpendicular to the medium running direction. It is disposed above the travel path of the medium 1 in a state where the medium 1 travels.

FIG. 7 is a circuit diagram showing a detection circuit built into the detection device 52, in which the sensor output voltages E and s of the sensor section 55 including the pixel elements 53 and 54 are input to the child terminals of the comparator 56, and One terminal of the comparator 56 is connected to the power supply voltage Vo through two resistors R.

Voltage Eo divided by R12 = Rtz・Vo / (
R11+R1□) is input as the slice level.

In the above configuration, the irradiation light L11 from the light emitting element 53 is reflected by the medium 51, and the reflected light L12 is transmitted to the light receiving element 54.
By receiving the light L12, a sensor output voltage Es corresponding to the intensity of the reflected light L12 is output. This sensor output voltage E
The change in s with respect to the position of the traveling medium 51 is the eighth
It will look like the characteristic diagram in the figure. And this sensor output voltage Es
is a predetermined slice level E. If it is higher, the comparator 56 outputs an ON signal indicating that a medium is present, or an OFF signal indicating that there is no medium if it is lower, as a detection signal.

As a result, the presence or absence of the medium 51, that is, whether the medium 51 is passing is detected.

<Problems to be Solved by the Invention> However, the detection device with the above configuration simply uses the slice level E set in advance. In order to detect the presence or absence of the medium 51 based on
The detection position of the medium 51 differs depending on the reflection characteristics of the medium. For example, between plain paper and an OHP sheet, as shown in FIG. 8, the slice level E is reached faster in the case of plain paper (solid line) with more diffused reflection than in the case of the OHP sheet (broken line) with less diffused reflection. reach. In other words, the detection position Dr for plain paper
There is a gap in the distance statement between the detection position D2 of the OHP sheet and the detection position D2 of the OHP sheet. Therefore, when the printing start position on the medium is determined based on the detection signal of this detection device.

Due to the reflective characteristics of the medium, a shift occurs in the printing start position.

In addition, in thermal transfer printers, etc., it is necessary to correct printing energy according to the degree of ink adhesion depending on the type of medium, or because the above-mentioned detection device cannot distinguish the type of medium, correction control of printing energy is necessary. cannot be used for.

The present invention was proposed to solve the above problems, and
It is an object of the present invention to provide a medium detection device that can determine the type of medium based on the reflection characteristics of the medium.

(Means for Solving the Problems) In order to achieve the above object, the medium detection device of the present invention has the following features:
A plurality of light receiving elements were provided to receive reflected light from the medium at different reflection angles.

<Operation> According to the above configuration, the intensity of the reflected light received by each light receiving element changes depending on the reflection characteristics of the medium.

Therefore, since the 0N10FF state of the detection signal from each light receiving element changes, the type of medium can be determined based on the 0N10FF state of the detection signal.

<Example> Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a schematic diagram of a medium detection device according to the present invention, as seen from the front in the direction in which the medium 1 travels.

As shown in the figure, the medium detection device 2 (hereinafter simply referred to as the detection device 2) includes a light emitting element 3 such as an LED, and a plurality of, for example two, light receiving elements 4.5 such as a phototransistor. Each element 3, 4.5 is arranged above the traveling path of the medium 1, with the elements 3, 4.5 arranged in a plane perpendicular to the medium traveling direction.

The light emitting element 3 irradiates the medium 1 with irradiation light L1 at an incident angle θ. And the above two light receiving elements 4, 5
is the reflected light L from the medium l of the above irradiation light.2. L
: Receives I respectively. The reflection angle of the reflected light L2 received by the first light receiving element 4 among the two light receiving elements 4 and 5 is 0.
□ indicates the above irradiation light.

The reflection angle θ3 of the reflected light L3 received by the second light-receiving element 5 is set to an angle that differs from the incident angle 01 by a certain angle, for example, a larger angle. The arrangement of the light receiving element 4.5 is appropriately set so that the detection device 2 functions as described below.

Each of the above elements 3, 4.5 is as shown in the circuit diagram of FIG.
It is connected to a detection circuit built into the detection device 2. As shown in the figure, a power supply voltage V is applied to the light emitting element 3, the first light receiving element 4, and the second light receiving element 5 via resistors R+, R2, and R*, respectively. As a result, each element 3,
4.5 and resistors R, , R2, R2, reflected light L2. Sensor output voltages E t and E z are output according to the intensity of L3.

These sensor output voltages E I and E 2 are respectively input to the child terminals of comparators 7 and 8, and one terminal of each of the comparators 7 and 8 is connected to the power supply voltage V through two resistors R, .
Voltage E divided by R4: l = R4V/ (R:,
+R, ) or is input as a slice level.

The above detection circuit causes an OFF signal from the comparator 7.8 when the sensor output voltage E1E2 is below the slice level E:l, and an ON signal when the sensor output voltage E, E2 is higher than the slice level E3. Output as a detection signal. That is, the resistors R2 and R in the above detection circuit
,'s, R,4 are set appropriately, the reflected light L2. When the intensity of L3 is higher than a predetermined level, the detection signal from each light receiving element 4.5 can be turned ON.

Next, the detection action of the detection device 2 having the above configuration will be explained using the schematic diagram of FIG. 3.

As shown in FIG. 3(a), when a medium with a lot of diffuse reflection, for example plain paper 1a, travels below the detection device 2, the spread angle φ of the reflected light is about 80 degrees, so each light receiving element The intensities of the reflected lights L 2 and L 3 received by the sensors 4 and 5 both become higher than a predetermined level, and each detection signal turns ON.

On the other hand, as shown in FIG. 3(b), when a medium with little diffuse reflection, such as an OHP sheet 1b, travels below the detection device 2, the spread angle φ2 of the reflected light is about 20 degrees, so the second The intensity of the reflected light L3 received by the light receiving element 5 becomes almost zero. Therefore, the detection signal from the first light receiving element 4 is O
N, the detection signal from the second light receiving element 5 is turned OFF.

Moreover, if there is no running medium l, naturally both detection signals will be OFF.

FIG. 4 summarizes the 0N10FF states of the above detection signals, and as can be seen from this figure, each light receiving element 4.
Based on the 0N10FF state of the detection signal from 5, it is possible to detect the presence or absence of the medium 1 and at the same time to determine the type of the medium 1. That is, the type of medium 1 can be determined from the reflection characteristics of the medium 1.

In the above embodiment, two light receiving elements 4 and 5 are provided to distinguish between the two types of media 1, or a larger number of light receiving elements 50 are provided as shown in the schematic diagram of FIG. By receiving the reflected light L4 at various reflection angles, more types of media 1 can be identified based on the 0N10FF state of the detection signal from each light receiving element 50.

In the above embodiment, each element 3, 4.5 is arranged in a plane perpendicular to the medium running direction, but the arrangement is not limited to this. Also, the number of light emitting elements 3 is not limited to -.

<Effects of the Invention> As described above, according to the medium detection device of the present invention, it is possible to detect the presence or absence of a medium and at the same time to determine the type of the medium.

Therefore, if the medium detection device of the present invention is installed in a printer or the like,
By correcting the deviation in the detection position caused by the difference in the reflection characteristics of the medium according to the determined type of medium, it is possible to eliminate the deviation in the printing start position.

Furthermore, the printing quality can be kept constant by using the correction control of printing energy according to the type of medium.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the embodiment, Fig. 2 is a detection circuit diagram in the embodiment, Fig. 3(a),
(b) is a schematic diagram explaining the detection action; FIG. 4 is a diagram showing the 0N10FF state of the detection signal;
6 is a schematic diagram showing another embodiment, FIG. 6 is a schematic diagram showing a conventional example, FIG. 7 is a detection circuit diagram in the conventional example, and FIG. 8 is a characteristic diagram in the conventional example. 1 (la, lb)...medium, 2...medium detection device. 3... Light emitting element, 4,5.50... Light receiving element. Ll...irradiation light, L2, L:l,l,,4...
reflected light. Patent applicant Oki Electric Industry Co., Ltd. Agent
Patent Attorney Funa Tachibana Kuni Rule Diagram (b) No. 7 Symbol? 7 pla 4 dig? 4 Shiba Al Otsuso Figure 3 ψ uJ-”

Claims (1)

[Scope of Claim] A device comprising a light-emitting element and a light-receiving element, detecting a medium by reflecting irradiated light from the light-emitting element on a medium, and receiving the reflected light with the light-receiving element, comprising: What is claimed is: 1. A medium detection device comprising a plurality of light receiving elements that receive reflected light having different reflection angles.